This invention relates to precise repositioning of a knife surface relative to an anvil surface. Although the invention is described as most useful to deactivate elastic portions in stretch laminates containing elastic, the precise repositioning of two rotating surfaces can be applied in other manufacturing techniques and environments.
Disposable diapers are typically equipped with elastic strands in different areas of the product. Some applied elastics, such as leg elastics, encircle the leg-holes. Other elastics are applied across waistbands. These strands of elastic are typically captured with adhesive between two layers of non-woven materials. In areas where adhesive is applied during the laminate formation, elastic adheres to the laminate and is retained in position to provide a stretchable quality to the laminate. In areas where elastics are applied, but no adhesive is applied, the elastic is free to snap back in the laminate and provide areas of relative inelasticity in the laminate. In this fashion, disposable products can be applied with alternating areas of elasticity and inelasticity, for instance across a waistband.
In one method of manufacture, the diapers are produced in an orientation whereby product flow is in the form of a single continuous web and the direction of travel is at a right angle with respect to what would be described as the crotch line of the diaper, i.e., the normal direction of product flow is parallel to the waist as opposed to parallel to the crotch.
The shirring effect created by elastic strands when laminated with any flexible fabric is well known. However, to have this shirring effect applied to the crotch of a pant-type garment can be undesirable. The elastics create a contractile force, which tends to distort the garment at this location, thereby reducing the garment's aesthetic appeal, effectiveness and comfort. Thus various methods of reducing or eliminating the effects of the elastic tension normally occurring at the crotch have been attempted. These methods include the elimination of the adhesive bond between the strands and the liner materials described in U.S. Pat. No. 5,745,922 as “unsecured space” as well as various methods of cutting the strands to eliminate their effects.
As mentioned, one method of eliminating the undesired effects of the elastic strands which cross the crotch region is to sever them. This method is described in U.S. Pat. No. 5,660,657. Unfortunately, such severing usually requires the introduction of a transversely extending cut, which can result in a loss of web tension in the severed part of the carrier web. This also creates an undesirable opening in the diaper backsheet. A proposed solution for this problem is taught in U.S. Pat. No. 5,707,470, wherein an ultrasonic device is used to sever the elastic members, while the carrier webs which encapsulate the elastics are left intact. See, also, U.S. Pat. No. 5,643,396. Another problem associated with such severing lies in the tendency of the unsecured severed ends of elastic to retract to some point beyond the limits of any adhesive pattern. Thus, the elastic strands are not controlled or anchored near the ends of the adhesion pattern and may snap back to further into the adhesive pattern. This results in an incomplete elastic pattern and poor product characteristics.